The introduction to object-oriented concepts in the lesson titled "Object-oriented Programming Concepts used a bicycle class as an example, with racing bikes, mountain bikes, and tandem bikes as subclasses. Here is sample code for a possible implementation of aBicycle
class, to give you an overview of a class declaration. Subsequent sections of this lesson will back up and explain class declarations step by step. For the moment, don't concern yourself with the details.public class Bicycle { // the Bicycle class has three fields public int cadence; public int gear; public int speed; // the Bicycle class has one constructor public Bicycle(int startCadence, int startSpeed, int startGear) { gear = startGear; cadence = startCadence; speed = startSpeed; } // the Bicycle class has four methods public void setCadence(int newValue) { cadence = newValue; } public void setGear(int newValue) { gear = newValue; } public void applyBrake(int decrement) { speed -= decrement; } public void speedUp(int increment) { speed += increment; } }A class declaration for a
MountainBike
class that is a subclass ofBicycle
might look like this:public class MountainBike extends Bicycle { // the MountainBike subclass has one field public int seatHeight; // the MountainBike subclass has one constructor public MountainBike(int startHeight, int startCadence, int startSpeed, int startGear) { super(startCadence, startSpeed, startGear); seatHeight = startHeight; } // the MountainBike subclass has one method public void setHeight(int newValue) { seatHeight = newValue; } }MountainBike
inherits all the fields and methods ofBicycle
and adds the fieldseatHeight
and a method to set it (mountain bikes have seats that can be moved up and down as the terrain demands).